Remote control key switch



Nov. 20, 1956 R. c. CRESSMAN ET AL 2,771,521

REMOTE CONTROL KEY swncn Filed Nov. 30. 1954 [h vent: 02 8: Robert C.Cr'essman, far/ F Re/fiman, by W 4. AW 77-: 9/) A t L, orn gy UnitedStates Patent Ofiice 2,771,521 REMOTE CONTROL KEY SWITCH Robert C.Cressman and Earl F. Reihman, Warwick, R. I.,

assignors to General Electric Company, a corporation of New YorkApplication November 30, 1954, Serial No. 471,976 2 Claims. (Cl. 200-42)This invention relates to improvements in electrical switches and inparticular to a single-pole, double-throw, momentary-contact,normally-open switch which is actuated by a separate key member ofspecial design. It is possible to utilize the key member as part of theelectrical circuit since this switch is for use in low-voltage controlcircuits as for the operation of on-off relays for the remote control ofresidential lighting circuits and the like.

In ordinary residential installations now in use it is customary to wirethe lighting system from the lighting fixtures to the controllingwall-mounted switches with suitable high-voltage cable such as armoredor non-metallic sheathed cable, which is adapted to operate under thefull voltage with which the system is supplied, for example, 110 volts.Within recent years remote control wiring systems have been gainingpopularity since they enable the use of an increased number ofcontrolling switches at only a small additional cost over theconventional wiring systems.

The switch of the present invention has been primarily designed tooperate in a low-voltage remote control wiring system operating at 24volts. In such a system a relay which is actually a small two-coilsolenoidoperated switch is mounted in one of the knock-out openings in astandard outlet box which supports a lighting fixture to be remotelycontrolled. This means that it is unnecessary to run high-voltage cablefrom the relay to the several control points or switches. Consequently,a great deal of expense is saved in wiring the lighting fixture inasmuchas low-voltage conductors, for example bell wire, may be run from therelay to the controlling switches. The average residence requires onlyone transformer to furnish the 24 volt power necessary to operate theremote-control relays regardless of the number of relays installed. Analternate arrangement would be to mount the transformer and a group ofthe relays in a single gang box near the service entrance switch. One ofthe early type of momentary-contact switches for use in a remote controlwiring system is shown in the Smith Patent No. 2,587,399, while an earl,remote control relay is shown in the Hutt Patent No. 2,324,844 both ofwhich are assigned to the same assignee as is the present invention.

In order to effect the wide acceptance of a remote control wiringsystem, it is understandable that a complete wiring system must be madeavailable in order to accommodate the particular wiring problems anddesired conveniences of the consumer. Consequently, it has been foundnecessary to produce a tamper-proof switch which must be operated by aspecial key for use in public places such as auditoriums, theaters,churches, as well as in outdoor lighting and outlet circuits, and powertool and other electrical equipment circuits in home workshops. This keyswitch makes it possible .to lock selected circuits in a remote-controlwiring system, thereby making the switches safe from small children andpractical jokers.

The principal object of this invention is to provide a key operatedlow-voltage switch for use in a remote control wiring system.

A further object of this invention is to provide a lowvoltagemomentary-contact key switch with a centering 2,771,521 Patented Nov.2t), 1956 spring that will act as a guide means during the insertion ofthe key in the switch housing.

A still further object of this invention is to provide a low-voltagemomentary-contact key switch with a centering spring that exerts a forceagainst the cover of the switch housing to press it against the mountingstrap in order to correct any loose fitting conditions between themating parts.

Our invention will be better understood from the following descriptiontaken in connection with the accompanying drawing and its scope will bepointed out in the appended claims.

Figure 1 is an exploded view of a low-voltage momentary-contact keyswitch embodying our invention, showing also the special design of thekey.

Figure 2 is a cross-sectional elevational view taken transverselythrough the center of the key switchof Figure 1.

Figure 3 is a simplified wiring diagram of a remote control lightingsystem in which is incorporated the subject key switch.

Figure 4 is a partial cross-sectional bottom plan view of a key switchembodying our invention taken on the lines 44 of Figure 2 showing inparticular the cooperation between the centering spring and the key withrelation to the cover of the switch housing.

Referring in detail to the drawing, Figure 1 shows in detail the partswhich make up the key switch 10 that embodies our invention. First,there is a recessed base 11 molded of a suitable insulating material andhaving a'bottom wall 12 and opposite side walls 13 and end walls 14. Theside walls 13 are provided with upwardly extending notches 15 and 16 ofdissimilar size, while the adjacent end walls 14 have their upper edgesarranged below the upper edges of walls 13 so that the cover 20 of theswitch housing is supported in the notches 15 and 16 as well as on theupper edges of the end walls 14, as will be better understoodhereinafter. A center contact 17 is mounted by means of a hollow rivetits on the raised shelf 19 formed onthe bottom wall 12 of the base. Sidecontacts 21 and 22 are mounted in openings formed through the bottomwall 12 to be symmetrically spaced from the longitudinal axis of thecenter contact 17 as well as around the inner end of said centercontact. In actual practice a 4-inch color-coded pigtail lead is securedto each of the contacts 17, 21 and 22 in a manner which is well known inthis art. 23 is threaded into the hollow rivet 18 and soldered thereinwhile the remaining two leads 24 are joined to flush-type recessedterminals of contacts 21 and 22 formed on the bottom of the base 11.

The cover 20 is also a box-like part molded from a suitable insulatingmaterial and it is of a size to enclose the top opening in the base 11so as to form a hollow switch housing. The outer appearance of the cover20 is made to conform to a standard remote control pushbutton switchalthough it should be appreciated that this does not form a part of thepresent invention and that modifications may be made in this detailwithout aifecting the invention claimed herein. Trunnion-like members 26and 27 are located on the sides of the cover 20 to mate with the notches15 and 16 respectively. It should be understood that the mating parts15, 26 and 16, 27 are made of diiferent sizes so that it is not possibleto assemble the cover 20 in an incorrect manner. If by chance the cover20 were reversed from the position shown in Figure 2 then it would notbe possible to apply the mount- For instance, the lead wireing strap 3%)over the cover so that the strap could be staked. to the base 11 to forman assembled switch. A keyhole 31 is formed through the top face of thecover 29 to communicate with the interiorof the cover 2%. A generallyC-shaped boss 32 is formed from the inner'surface of the top Wall of thecover 20 to-straddle the enlarged rounded end 33 of the keyhole 31.

The mounting strap as seen in Figure l is. generally of rectangularsheet metal construction having downwardly extending end members. 28with corner stakes 29. When the cover 20 is properly seated on thebasell and the strap 30 is installed the stakes29 are bent under theabutments 45 on the end walls 14 of the base to form a completelyassembled switch.

Turning now to a consideration of the key 35 best shown in Figures 1 and2, the key is formed at one end with a handle portion 36 and at itsopposite end with bifurcations 37 and 38 of difierent widths. Thesmallest leg or bifurcation 37. is of a size to project through anopening 34 located in the inner end of the center contact 17. A notch 39is cut in one edge of the stem or shank of the key adjacent the handle36. I Consequently, the key cannot be inserted into the switch housingincorrectly for then the bifurcation 38 would be seated on top of thecenter contact 17 and the notch '39 would be outside of the cover 20 sothat the key could not turnand close the circuit between the centercontact 17 and either one of the side contacts 21 and 22. Therefore, itshould be appreciated that only a special key offthe nature of key 35could be used to operate the subject switch.

In the wiring diagramof Figure 3, 50 is a conventional step-downtransformer with the primary connected to the 110 volt power supply, andthe secondary delivering 24 volts to the control circuit. The controlcircuit comprises a parallel arrangement of two momentary contactpush-button switches 51 and a key switch 10 which embodies the inventiondisclosed herein. Each switch is capable of actuating either the On orthe Off coil of the relay 52 so as to open or close the lighting circuitwhich is directly connected across the 110 volt power supply and shownas comprising the lamp load 53.

In actual practice a remote control switch is mounted in a switch strap(not shown) which in turn is fastened by a suitable screw means to .arecessed switch box embedded in a wall structure or as. an alternativespecial brackets (not shown) are available for supporting the switchesin a wall since it is not necessary to mount the switches in a closedbox because of'the low voltage that is being used in the relay circuits.Remote control switches may either be arranged vertically orhorizontally. This fact presents a problem in the design of key switchesof the type disclosed herein foriif the switch were mounted verticallyand the key were left in the switch it will be appreciated that the keywill naturally pivot in the switch housing due to its own weight andthereby close the switch and hold it closed. Only a momentary contact isnecessary between the switching parts in order to actuate the relay toswitch the power circuit for the particular lighting fixture. If theswitch is held closed by leaving the key therein, the coils of the relaywill tend to overheat and after a period of time the relay is likely tofail due to the excessive heat. For this reason, a thin metal centeringspring 40 generally of rectangular shape encompasses the boss 32 in thecover 20 and is' provided with a pair of spaced fingers 41 arranged atthe sides of thekeyhole 31. The ends 42 of the fingers 41 adjacent thekeyhole 31 diverge outwardly to form wedge surfaces that permit the key35 to enlarge the spring as shown in Figure 4 so that there is nolooseness between the key and the fingers 41 of the centering spring. Ananchoring leg 43 is formed integral with the spring 40 and it is bent atan obtuse angle away from the main portion of the spring to be seated onthe ledge 44 of the shelf 19 in the base of the switch housing. Theanchoring-leg 43 is of such a length that when the cover-20 is seated*on the base 11 the leg 43 will be placed under compression so that inthe assembled switch the springing effect of the leg 43 tends to holdthe cover 20 against the mounting strap 30 of the switch to remove anylooseness between these parts.

Accordingly, it will be appreciated that when the key 35 is inserted inthe keyhole 31 of the switch housing the key will spread the fingers 41of the centering spring apart and the bifurcation 37 will extendthroughthe opening 34 in the center contact 17 0f the switch. As the key35 is turned in the switch, the centering spring 40 will be deformed sothat the key will close the circuit to operate either the On or the Offcoil of the relay to operate the lighting circuit. When the turningforce is removed from the handle of the key, the centering spring 40will naturally return the key to the neutral position with thebifurcation 38 centered between the sidccontacts Ziand 22. Anotheradvantage of the centering spring is to provide a slight resistance tothe turning movement of the'kcy in the switch so as to improve the feelof the key to correspond to the action of a conventional lock and key.

Consequently, having described our invention of a lowvoltage key switchfora remote control wiring system, it will be readily apparent to thoseskilled in this art that this switch has a minimum number of parts whichare simple in construction and easy to assemble by mass productionmethods. This switch is also reliable in operation and made to withstanda great deal of use and abuse as well as being attractive in appearanceand low in cost. While we have chosen to illustrate our presentinvention in a flush mounted switch, it should be readily apparent thatthis invention is not limited to such a switch and that the claims ofinvention found hereinafter are intended to cover all modificationswhich are within the true spirit and scope of this invention.

What we claim as new, and desire to secure by Letters Patent of theUnitedStates is:

l. A low voltage momentary-contact key switch comprising a hollowhousing with a center contact and one or more side contacts mountedtherein, the center contact having an aperture to receive a portion of akey member -so that the key maypiv-ot therein to make contact with oneor the other of the side contacts, and a centering spring supported inthe housing and adapted to hold a key member in a neutral open circuitposition when the key 15 left in the switch, the said centering springbeing supported by an anchoring leg from the bottom portion of thehousing, while the main portion of the spring encompasses a boss formedas an integral part of the top portion of the housing to provide apairof spring fingers adapted to engage and resist any turning movementof the key.

2. A low voltage momcntar3-contact key switch comprising a hollowhousingwith a common contact and one or more side COIlitiCtSiTlOlll'llCdin the bottom portion thereof, the common contact having an aperture toreceive a portion of a key member so that the key may pivot therein tomake contact with one or the other of the side contacts. a keyholeformed through ire top surface of the switch housing and an inner hossintegral with the top portion of the switch housing and located adjacentone end of the said keyhole, and a centering spring with an anchoringleg supported in the bottom of the housing. while the main portion ofthe centering spring encompasses the said inner boss, one side of themain portion of the said spring being split and formed with springfingers adapted to engage the sides of a kcyinscrtcd into the switchhousing.

References Cited in the file of this patent UNITED STATES PATENTS970,410 Wilson Sept. 13, 1910 1,143,676 Williams June 22, 1915 1,291,722Barnes Jan. 21, 1919 1,977,887 Murray Oct. 23, 1934

